Bone doesn't rotate at right axis
You have three options,

1) what you want is to rotate bone on custom axis, for this please see 
Rotate object on axis between two points

2) if (1) this is cumbersome then i'll suggest, join all mesh (KFlügelR, FlügelL, Vogel, FlügelL, KFlügelL) together (select all mesh and do ctrl+j ). Then assign the armature to this joined mesh, use auto weight for first try . ( if you do not know how to do this then just ask :) )

3) Make the mesh so that its pivot is aligned to the bone orientation.

I'll suggest option (2), as it should be the right way anyhow.